After Donald Trump’s victory on Tuesday, longtime skeptic Robert F. Kennedy Jr. is poised to have tremendous influence on how the United States regulates and distributes its vaccines.

Kennedy has championed the dismissed idea that vaccines cause autism for decades and founded the nonprofit Children’s Defense Fund to promote theories linking vaccines to other conditions. Other leaders have aligned with Trump The Make America Healthy Again movement they also have a history of anti-vaccine advocacy. Kennedy fired back more inflammatory anti-vaccine rhetoric recently, instead emphasizing his desire for more transparency and data around products. It’s not clear exactly what data they’re looking for.

“If vaccines work for someone, I won’t take them,” he said MSBNC Wednesday. “People should have a choice and that choice should be based on the best information.”

State health officials decide which vaccines to recommend in schools and for the broader population, but they rely on the Food and Drug Administration and the Centers for Disease Control and Prevention to regulate and recommend vaccines, respectively. While Kennedy’s game plan may not include taking vaccines off the market, health experts worry that he could influence agencies to slow approvals, fill advisory committee seats with skeptical peers and generally could spread misinformation.

What Kennedy is able to do will depend on who ends up leading the FDA, the CDC and the larger Department of Health and Human Services. The main barriers against him going vaccine rogue are pushback from the public, Congress, the drug industry, and other government employees.

“There’s nothing stopping it, we just have to deal with the consequences,” said Bryant Godfrey, a partner at Foley Hoag and a former FDA regulatory attorney.

The FDA doesn’t recall products “willy-nilly,” Godfrey said. A vaccine must present a clear safety concern for the agency to consider forcing companies to remove it. Manufacturers could easily sue if an FDA influenced by RFK Jr. penalize a product without evidence.

“If the FDA reversed its decision to approve a vaccine in the absence of any rigorous scientific evidence, it would be rejected by even the most conservative Supreme Court,” said Lawrence Gostin, a professor of global health law at Georgetown University.

Kennedy could push FDA reviewers to request additional data from companies submitting their vaccines for approval, although the submission process is already rigorous. It’s unclear what impact that might have, as he didn’t make clear what additional data and vaccines he’s looking for.

If Kennedy were to undermine vaccines through the FDA, he would face backlash both within the agency and from powerful industry interests. The CDC, on the other hand, is more vulnerable to its influence.

One of the biggest barriers to vaccine approval at the CDC is the Advisory Committee on Immunization Practices. The group makes vaccination recommendations that apply to the entire US population. Currently, committee members are independent experts who study dozens of research papers and compete against each other to make recommendations. But that could change under Trump.

To be appointed to the committee, ACIP members must be approved by the HHS secretary—who is handpicked by the president. Gostin said Trump or Kennedy could quickly fill ACIP with Trump loyalists and vaccine skeptics, which could leave the group ill-equipped to provide accurate vaccination recommendations. ACIP recommendations inform insurers whether they should cover a particular vaccine, so panel stacking could also affect vaccine affordability.

The role is tough, said pediatrician Paul Offit. When he helped develop a vaccine for a virus that causes stomach flu, the process from initial studies demonstrating its effectiveness to final approval took 26 years. Every potential vaccine is treated similarly, even a disease as mundane as chicken pox, Offit said.

“If you really want to be informed about (chickenpox), then you would have read the 300 papers that have been published about it, which means you would have had to have some background in neurology and immunology and statistics and epidemiology, which that most people don’t have — and frankly, most doctors don’t,” said Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia. “That’s why they’re looking at these expert committees.”

Further disruption of federal vaccine policy could come through the courts. In June, the US Court of Appeals for the Fifth Circuit UNDERMINED the authority and constitutionality of advisory committees such as ACIP. It ruled that the Affordable Care Act could not mandate coverage of preventive care such as contraceptives or drugs like PrEP that prevent HIV, although the decision for a national mandate was rejected in a lower court.

If the Supreme Court takes up the case, it could be like pouring gasoline on a campfire, said Leighton Ku, a professor of health policy at George Washington University. Administrative agencies like the FDA are already reeling from the Court’s ruling on the Chevron doctrine.

“(Kennedy) can step in. There is no doubt that he can intervene. How he can step in are complicated … but I’m willing to believe he (will) if motivated enough,” Ku said.

The easiest thing for Trump and Kennedy to do to dismantle vaccine policy would be to continue their current actions: speak from the pulpit and influence the public’s perception of the safety and effectiveness of these immunizations. Americans are increasingly unlikely to say that childhood vaccines are important and several jurisdictions are granting exemptions.

“RFK already has influence in discouraging people from using vaccines, even though he’s not in the government at all right now,” Ku said.

That soft power is likely to produce the biggest changes and only increase if Kennedy takes an official federal position, said former HHS Secretary Kathleen Sebelius. During her tenure from 2009 to 2014, Sebelius met with the vaccine skeptic several times and each time reiterated her position. She doesn’t know how Kennedy will do”savage” in federal health agencies. But she is worried nonetheless.

“He was convinced that we weren’t getting accurate information from the CDC, that we were being misled by the science, that we just needed to fire people and bring in new evidence,” she said.